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Monday, August 27, 2012

Waterfall Climbing Fish

By Patrick Cooney

Patrick Cooney

My perch atop a 100-foot waterfall affords a small break in the tropical rainforest canopy that frames a distant golden-sand Caribbean beach. I crouch in the heavy humid air, anxiously awaiting the arrival of a fish that is reaching the tail end of an arduous journey incredibly disproportionate to the creature’s size.

A drop of salty sweat slips into my eye and clouds my vision, but not before I catch a glimpse of what I trekked so far to witness. Like being hauled up by a rod wielding angler, a turquoise and tangerine infused sirajo (“si-rah-ho”) goby defies gravity as it nears the crest of the waterfall from below. This jewel of the river strains against the current, tenuously gripping the slick bedrock with a single suction-cup-like fin. One wrong move and this sojourner will surely plunge into hungry mouths of predators in the distant pool below. Little by little, the long distance traveler lunges forward, each a victorious step not only in the struggle to escape hungry mouths, but also to perpetuate the species in the face of drastic declines.

The sirajo goby! (Patrick Cooney)

Climbing a waterfall is the last major hurdle of the specialized life cycle of a sirajo goby. Larvae hatch in high altitude streams and are rapidly swept to the sea during the tropical rainy season. Hitching a ride on ocean currents, juveniles store energy for a climb equivalent to a human scaling six Empire State Buildings. As tides deliver sirajos to river mouths, individuals fight a gauntlet to finally complete their journey in high mountain streams. These fish are built to climb and tall waterfalls are their domain, but artificial barriers, like dams with dry facades, are impassable obstacles.

Puerto Rico rising from the Caribbean Sea. (Patrick Cooney)

Puerto Rico, like a ship on the high sea, stoutly rises out of the Caribbean to almost a mile in elevation. The island was once an agricultural epicenter with sugarcane on the coastal plains and coffee production on steep mountainsides. Water was a necessity, thus dams of all sizes were built in almost every waterway. As these historic industries faded and others took hold, the human population ballooned, requiring the construction of more dams of even grander sizes. Although plantation dams became forgotten relics lost to the jungle, an absence of native fish in mountain streams acted as a constant reminder that derelict dams with dry escarpments were widespread and continued playing a sinister role in blocking goby migrations. With only six native freshwater fish species in Puerto Rico, any remnant of diversity is worth protecting, making the restoration of migration corridors imperative.

Dry dams block fish migration. (Patrick Cooney)

Endemic Puerto Rico boa constrictors lurked as I hunted down dams and sampled fish deep in the jungle where few people care to venture. With perseverance, and countless tubes of calamine lotion, I tracked down more than 300 dams that completely blocked sirajo goby migration from critical upstream habitat. Now, with this inventory of lost dams in hand, the Puerto Rican government is poised to remove dams and build fish passage devices to help restore historic migration corridors.

Back at the waterfall, the determined sirajo goby makes a final lunge into the shallows at my feet. The challenge for this individual goby was surmountable, but can the same be said for the bigger challenge of restoring historic goby populations? The fate of the sirajo is largely dependent on the fate of dams, and migration restoration represents the final hurdle this river jewel must overcome to once again be free to climb waterfalls in rivers throughout the Caribbean.

See the video below of an almost identical fish in Hawaii that was featured on a BBC special!